A two-wheeled vehicle denotes a vehicle that has two wheels such as a bicycle or a motorcycle and includes a vehicle body frame, a front wheel, a rear wheel, a suspension system, a steering system, and the like.
Since the balance of the two-wheeled vehicle is not maintained by only the front and rear wheels while parking, a driver stands the two-wheeled vehicle by standing a stand installed at a side of the vehicle body frame on the ground, and when traveling at a low speed and changing a traveling direction, the driver has to maintain the balance of the two-wheeled vehicle by a sole of driver's foot coming into contact with the ground.
Particularly, when the two-wheeled vehicle is turning, even though the vehicle body frame and the driver may turn while aligned, the driver generally has to tilt driver's body further inward or outward than the vehicle body frame is tilted to turn in order to maintain balance using centrifugal force and gravity while turning.
That is, when driving skill of the driver is immature in cornering the two-wheeled vehicle, the balance of the two-wheeled vehicle is not maintained and the two-wheeled vehicle thus falls down, and when a road is irregular or slippery due to rain, snow, or the like as well as when cornering, there is a problem in that the immature driver has a difficulty in maintaining the balance.
A stabilization device of a two-wheeled vehicle disclosed in Korean Laid-Open Patent Publication No. 10-2012-0027625 includes auxiliary wheels 25 and 35 in the middle of a frame for stabilizing the two-wheeled vehicle while traveling. Here, although levels of the auxiliary wheels, which are always in contact with the ground, are changed by shock absorbers 40 and 50, the auxiliary wheels may actually hinder turning due to continuous friction with the ground or different turning radiuses of the auxiliary wheels from that of a front wheel during turning.
Furthermore, Korean Laid-Open Utility Model Registration Application Publication No. 1999-0017351 discloses a motorcycle in which auxiliary wheel devices configured to maintain vertical balance of a vehicle body are installed. Although auxiliary wheels of the auxiliary wheel devices are lifted not to come into contact with the ground while traveling, the auxiliary wheels may not provide a function for improving turning stability during travel, and their use is limited to only a state in which the motor cycle is not traveling.